This invention generally relates to a cartoning machine and more specifically to an end flap sealing mechanism to close and seal the end flaps of cartons travelling along the conveyor of the cartoning machine.
Cartoning machines to which the present invention is applied are conventional ones which have been used in the packaging industry for years. The present invention is adaptable for use with cartoning machines which carry cartons in a horizontal, sloping, or vertical direction.
During the packaging of products using such cartoning machines, the cartons are erected and delivered into pockets between transport lugs that are carried on an endless chain conveyor. At least one end of each carton has open flaps to which a hot melt glue is applied at a gluing station. Downstream of the gluing station, a plow mechanism compresses the flaps together and holds them for a period of time sufficient to permit the glue to permanently set. The other end of the carton may also have flaps which are to be glued and plowed closed or may alternatively have tuck flaps which are closed by a conventional mechanism.
Prior flap closing mechanisms have included both stationary plows and movable plows. Stationary plows have been conventionally used to close the outermost end flap against the other end flaps as the carton, traveling along the conveyor, passes the stationary plow which is mounted adjacent the conveyor. The stationary plows have outwardly flared and, for example, downwardly tapered upstream ends which engage the outermost end flap and force it to pivot to a closed position as the carton moves along the conveyor. Downstream from the outwardly flared portion, the stationary plow includes a planar portion generally parallel to the ends of the cartons being sealed. This planar portion maintains compression on the end flaps of the moving cartons while the glue permanently sets.
One prior moving plow for folding the outermost end flap of a carton against the other end flaps of the carton after glue has been applied in a cartoning process is disclosed in U.S. Pat. No. 3,504,478 to Dieter and entitled AUXILIARY END FLAP SEALER FOR CARTONING MACHINE. The auxiliary end flap sealer of Dieter includes an end flap closer operating on a hinge mechanism actuated by a pneumatic cylinder. The end flap closer is positioned in the glue applying area of the cartoning machine and may be rotated approximately 90.degree. between a position in which the closer does not affect the position of the carton end flaps and a position in which the closer holds the end flaps in final sealing position. The closer is actuated only upon normal or emergency shutdown of the cartoning machine.
Another prior patent which discloses carton flap sealing is U.S. Pat. No. 4,480,421 to Rece entitled AUXILIARY FLAP SEALER FOR A CARTONING MACHINE. Rece discloses a mechanism to complete the gluing if gluing has been partially completed when the cartoning machine stops for some reason and to force and hold the flaps together until the glue sets. Specifically, Rece discloses a control system to determine whether glue has been partially or fully applied to the end flap of a carton when the machine has shut down for any reason. If glue has been partially applied then the control system causes the gluing application to be completed and a plow to be moved in an upstream direction to seal the carton. If the gluing operation was complete upon shutdown of the machine then no further glue is applied but the plow is moved in an upstream direction to seal the carton.
A movable plow is also known in which the plow is mounted adjacent the conveyor of a cartoning machine to reciprocate at a 90.degree. angle to the moving cartons. The plow has a top edge that is parallel to the path of the cartons moving down the conveyor. The top edge is adapted to engage and fold the outermost end flap of the carton inwardly to seal it against the other end flaps. One disadvantage of this design is that the plow must be moved back to its start-up position, below the lower edge of the incoming carton, before the conveyor may be caused to move the incoming carton into position adjacent the movable plow. If the next carton is moved toward the plow before it is fully retracted then the flaps of the carton will hit the plow and either damage the carton or move it out of its proper position on the conveyor.
It will also be appreciated in connection with carton closures using hot melt glues that it is desirable to close the carton flaps immediately after glue applications, thus avoiding the possibility that the glue will set up before such closure and the seal will not function properly.
Accordingly, it has been one objective of the invention to provide an improved movable plow mechanism for folding and sealing the end flaps of a carton as the cartons move past the plow to increase the speed of the cartoning operation.
It has been another object of the invention to increase the amount of time that the end flaps are initially held under compression by a movable plow to minimize end flap relaxation and prevent end flaps from unfolding and buckling against parts of the cartoning machine before the cartons are moved by the conveyor downstream to a location where the end flaps engage a stationary plow.
It has been another objective of the invention to decrease the time delay between hot melt glue application and carton flap closure to reduce seal inconsistencies.